In general, when extruding a billet made of a metal material, for example, aluminum or its alloy, from an extrusion press device, a hydraulic cylinder is used to drive a main ram. At the front end of the ram, an extrusion stem is attached. A billet is inserted by a billet inserter into a container in the state where the container is pushed against a die. The main ram is made to advance driven by the hydraulic cylinder whereby the billet is pushed by the extrusion stem. Therefore, a shaped product is extruded from the opening part of the die. After extruding the billet, the container is made to retract somewhat by the container cylinder and the discard (remaining part of the billet) is pulled out from the container. The work is called “container stripping”. After the discard is removed from the container, the main ram and container start to retract. Next, the blade of a shear device is inserted between the container and die to cut off the billet remaining at the die surface (that is, the discard). After that, the main ram is made to further retract to completely pull out the extrusion stem from the container and return the extrusion stem to its initial position. The next billet is inserted into the container and the extrusion operation of the next extrusion cycle is proceeded to.
An extrusion press device is provided with a billet transport device. As a specific example of such a billet transport device, the prior art shown in FIGS. 4 and 5, PLT 1, etc. may be mentioned. The billet transport device 124 of the prior art of FIGS. 4 and 5 is comprised of a billet heater 121, free rollers 122, a billet loading device tray 123, rails 125, a billet pusher 126, a billet loader 127, etc. The extrusion press device is comprised of an end platen 101, container 103, extrusion stem 105, main crosshead 106, main cylinder 107, main ram 108, side cylinder 109, container cylinder 111, etc. As seen in the prior art of FIG. 4, when using the extrusion press device to perform an extrusion operation, the starting material, that is, the billet, is extruded to obtain a product. First, the billet 110 is preheated inside the billet heater 121. Using a start command of the extrusion cycle, that is, a “billet call” (instruction from extrusion press demanding billet from billet heater), a billet 110 leaves the billet heater 121, passes over the free rollers 122, then is placed on the billet loading device tray 123. The billet loading device tray 123 carrying the preheated billet 110 moves over the rails 125 and moves close to the extrusion press device. The billet is pushed by the billet pusher 126 and moves to the roller part of the billet loader 127 (insertion rollers 133, see FIG. 5). After that, the billet loader 127 is used to move the billet to the center of the extrusion press device and insert it into the container 103.
Referring to FIG. 4, the flow of operation of billet transport of the prior art will be explained. The following (1) to (8) are shown in FIG. 4 as a reference display of the corresponding flow of operation.
(1) A billet 110 is preheated by the billet heater 121, then moves over the free rollers 122 and is placed on the billet loading device tray 123 at the position S.
(2) At the billet movement device 124, the billet loading device tray 123 carrying the billet 110 passes over the rails 125 and is moved to a position T near the extrusion press.
(3) The billet pusher 126 pushes the billet 110 on the billet movement device tray 123 to move it to the billet insertion device 134 of the billet loader 127.
(4) The billet pusher 126 is retracted.
(5) The billet loader 127 moves to the extrusion press center (see imaginary lines of 127 and 134).
(6) At the billet insertion device 134 of the billet loader 127, the billet insertion member 132 pushes against the billet 110 and moves it over the insertion rollers 133 (see FIG. 5) to insert the billet 110 to the inside of the container 103.
(7) The billet loader 127 is retracted to the initial position.
(8) The billet insertion member 132 returns to its original position.
FIG. 5 shows details of the billet insertion device 134 of the billet loader 127. In the billet insertion device 134 of the billet loader 127, the insertion rollers 133 were single parts, that is, were not split but were integral rollers. Further, the insertion rollers 133 were not that large in diameter, so the arc-shaped grooves formed by the contact of the billet 110 and insertion rollers 133 were shallow, so the billet 110 could not be stably carried. To stably carry the billet 110, it was necessary to provide supports at the two sides of the billet 110 and clamp the billet 110 from the two sides. However, if trying to place the billet 110 on the insertion rollers 133 by an overhead type billet carrier 40, arms 41 of the overhead type billet carrier 40 (see FIG. 2) would interfere with the supports 131 preventing the billet 110 from being placed on the insertion rollers 133. Therefore, in the prior art, it was not possible to use an overhead type billet carrier 40 to utilize the top space and place a billet 110 on the billet insertion device 134. It was necessary to use the billet pusher 126. Further, there was chains (not shown in FIG. 5) for driving the billet insertion member 132 of the billet insertion device 134, rails 135, and wheel rollers 136 guided by the top and bottom rails 135 at the two sides of the insertion rollers 133, so the billet insertion device 134 became greater in width as a whole. In the billet loader of PLT 1 as well, the arms of the overhead type billet carrier interfered with the loader frames 22 and 23 of the billet insertion device, so the above problems arose.